Fluctuations in plankton community structure of endorheic soda lakes of southeastern Transbaikalia (Russia)

The aim of present research is to study the patterns of phyto- and zooplankton fluctuations in endorheic soda lakes (Uldz Gol-Torey Basin, southeastern Transbaikalia, Russia) under arid conditions because studied area is becoming increasingly arid. Plankton samples were collected in summer during time intervals with different lake water levels using standard hydrobiological methods. We detected four patterns of change in plankton communities with changing environmental conditions (increasing total dissolved solid, pH and temperature, and decreasing depth). The first pattern is characterized by a predominance of green algae, charophytes, diatoms and euglenophytes; the species composition and dominant zooplankton assemblage are the same in different years. The second pattern is characterized by a loss of cryptophyte and chrysophyte algae, a dominance of green and blue-green algae, a decrease in zooplankton species diversity, and an increased abundance of zooplankton, the dominant species are consistent over time. The third pattern exhibits marked decreases in phytoplankton diversity and density, a dominance of green algae and diatoms, a further decrease in the species richness of zooplankton, and increased abundance and biomass of some species. The fourth pattern is a marked by a reduction in plankton species diversity to a monospecific community.